HVAC Control Using PV Load and Comfort Thresholds

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Solution Overview

Problem

In residential and non-residential settings with grid-connected solar photovoltaic (PV) systems, there is a challenge in maximizing PV energy production and usage while minimizing electrical energy consumption from the grid, especially when PV energy is insufficient or not available, while maintaining a desired comfort level.

Innovation Solution

A control system dynamically adjusts the operation of Heating, Ventilation, and Air Conditioning (HVAC) systems based on current and future PV production, energy loads, energy prices, and comfort levels, increasing energy usage when PV generation is low and reducing it when energy is more expensive or abundant.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the HVAC system operates at high power mode to maintain desired comfort level, then the comfort level is maintained, but the electrical energy consumption from the grid increases

Engineering Contradiction:

Improvecomfort levelVSAvoidelectrical energy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The HVAC system dynamically adjusts its power mode (high, medium, low) based on real-time conditions including PV energy availability, grid energy prices, and comfort requirements. The controller continuously monitors these parameters and adapts the HVAC operation accordingly, transitioning between power modes to optimize the balance between comfort maintenance and energy consumption from the grid.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters by adjusting the power mode of the HVAC system based on varying conditions. When PV energy is abundant and grid prices are low, the system operates in high power mode. When PV energy is insufficient or grid prices are high, it transitions to medium or low power modes, thereby changing the energy consumption parameter while adapting to external conditions.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the HVAC system reduces energy usage to minimize grid energy consumption, then the electrical energy consumption from the grid is reduced, but the comfort level may deteriorate

Engineering Contradiction:

Improveelectrical energy consumptionVSAvoidcomfort level

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The controller continuously monitors comfort level parameters and uses this feedback to adjust HVAC operation. When comfort thresholds are approached or exceeded during low-power operation, the system receives feedback and adjusts its power mode accordingly to prevent comfort deterioration, ensuring that energy reduction does not come at the cost of unacceptable comfort levels.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary cooling or heating actions when PV energy is abundant and grid prices are low, operating in high power mode to pre-condition the space. This preliminary action stores cooling or heating capacity in the building thermal mass, allowing the system to operate at lower power modes during periods when grid energy is expensive or PV energy is insufficient, thereby maintaining comfort while reducing overall grid energy consumption.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If the system increases HVAC power consumption when net load is below threshold to maximize PV energy usage, then PV energy utilization is improved, but the net load increases

Engineering Contradiction:

ImprovePV energy utilizationVSAvoidnet load

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The system converts the potential harm of increased net load into a benefit by strategically increasing HVAC power consumption only when PV energy is abundant (net load below threshold). The additional energy demand is intentionally created to absorb excess PV generation that would otherwise be wasted or require expensive grid export, thereby converting the problem of excess PV generation into useful energy utilization.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system performs preliminary energy consumption actions during periods of high PV generation by increasing HVAC power mode. This preliminary consumption of PV energy during peak production times maximizes the utilization of renewable energy before it becomes excess, reducing the need to export energy to the grid or waste it, thereby improving overall PV energy productivity.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10247436B2Systems and methods for controlling operations of a heating and cooling system

Publication Date: 2019.04.02 SOLARCITY CORPORATION

AI summary

Techniques for controlling a heating, ventilation and air conditioning (HVAC) system at a site are disclosed. A disclosed method includes obtaining or calculating a net load at the site and obtaining a temperature of the site during a time period. The method further includes comparing the net load to a threshold load value and comparing the temperature to a lower threshold temperature or an upper threshold temperature. The method also includes determining one or more operation parameter values for the HVAC system based at least in part on the comparison of the net load to the threshold load value and the comparison of the temperature to the lower threshold temperature or the upper threshold temperature, and setting the HVAC system based on the one or more operation parameter values.